Productivity analysis of two spiral-wound membrane distillation prototypes coupled with solar energy

The use of solar energy to feed the MD desalination process is being evaluated at Plataforma Solar de Almeria, the largest European facility for solar energy research, located in SE Spain. A test bed for the evaluation of membrane distillation modules is under operation coupled to a field of static solar collectors. Different commercial modules and real-scale prototypes are tested in continuous operation and coupled with a solar thermal source, in order to obtain data in conditions closer to real applications than the tests performed at laboratory scale. This particular study shows an evaluation of two different modules using spiral-wound membranes, one with a liquid-gap configuration (built by Solar Spring) and the other with an air-gap configuration (built by Aquastill). An assessment of the influence of the operational parameters in the performance was done within the allowed ranges of operation of each prototype, with special attention to the temperatures and the feed flow rate. Also, the influence of the salinity was investigated using feed water with salts at different values of conductivity. The characterization of the systems is done based on the quality of the distillate, as well as the measured values of distillate production and thermal performance, choosing the specific distillate flux obtained and the gain output ratio (GOR) as performance indicators. The main results of the analysis are summarized and compared, discussing the particular operational experiences in each case.